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In this paper, the static response and normal/shear stresses of axially functionally graded exact super-elliptical beams are presented via a warping-included mixed finite element method. Super-elliptical axis geometry is derived over the exact functions of planar curves. The constitutive equations are obtained from three-dimensional elasticity theory. The mixed finite element formulation is enhanced by including the warping deformations via displacement-type finite elements on the cross-section. The two-noded curved mixed finite element has twenty-four degrees of freedom in total. Satisfactory results are obtained for the warping-included normal/shear stresses, displacements and reactional forces of axially functionally graded exact super-elliptical beams even with lesser degrees of freedom compared to the three-dimensional behavior of brick finite elements. As benchmark examples, the influences of high axial curvature, cross-sectional geometry and material gradation on the static response and stresses of axially functionally graded exact super-elliptical beams are investigated.

This article presents a new higher-order beam model. The present beam model is governed by differential equations that are similar to those present in some existing higher-order beam models; however, the present beam model makes use of a novel method of calculating the transverse shear stiffness, which facilitates the calculation of a shear-warping stiffness without the need for an assumed warping displacement field, and without introducing any additional kinematic variables. The present beam model also facilitates the recovery of the distributions of longitudinal normal stresses and transverse shear stresses. The authors postulate that the bending and shear terms in first-order shear deformation theory represent the first two terms in an infinite series that would constitute an ideal one-dimensional beam model, and it is suggested that the present beam model constitutes the first four terms in this hypothetical infinite series. The present beam model is solved for several example beams, and the results are compared with those of existing classical and higher-order beam models, as well as computational results from finite element analyses. It is shown that the present beam model is able to accurately represent deformed shapes and stress distributions pertaining to beams that exhibit non-trivial shear compliance as well as non-trivial shear-warping stiffness. In the case of laminated composite beams comprising a large number of laminae, the present beam model offers a level of analytical fidelity that is comparable to that of existing zigzag beam models; however, unlike zigzag beam models, the present beam model is equally well suited for the analyses of beams comprising any number of laminae.

The study presents an analysis of steel I-beam warping. The calculations were made for hot-rolled IPE200 hinged beams with different lengths. After determining load-bearing capacity using the GMNIA method, the beams were strengthened with bimoment restraints at each end. The changes in critical moment and load-bearing capacity were then evaluated. The study presents the manner in which the material and geometric imperfections have been determined. The GMNIA calculations were conducted using the Finite Element Method in Abaqus software. The results were then compared to results obtained with traditional methods and acquired from LT Beam software.

This research focuses on thermal deformations of thermoplast during three-dimensional printing. A filament acrylonitrile butadiene styrene was used, and the main focus was put on warping. Twenty-seven cuboids divided in six categories by their length, height, surface area, color, nozzle temperature and bed temperature were printed by Fused Filament Fabrication 3D printer. The whole process was captured by a thermal camera and the movies were used to analyze the temperature distribution during printing. All printouts were measured and scanned with a 3D scanner in order to highlight any abbreviations from the original digital models. The obtained results were used to formulate some general conclusions on the influence of selected parameters on the warping process. Based on the outcomes of the study, a set of guidelines on how to minimalize warping was proposed.

The article analyses the method of enhancing a steel beam by adding additional steel members like ribs. They are rigidly connected with both flanges in a plane parallel to the web. That plates reduces warping during in-plane bending of steel beam under lateral-torsional bucking. Different thicknesses of steel plates used as ribs and different cross-sections were taken into account. Calculations were conducted using FEM and ABAQUS CAE environment. The outcomes were compared with ones from previous studies which concerned an influence of endplates on load-bearing capacity of an I-beam.

In this paper, we investigate the coupling of Poisson’s and warping effect for a general asymmetric cross-section of Cosserat beam. We present the challenges and inconsistencies observed as a result of our attempt to couple the two effects. The fully-coupled Poisson’s transformation is then developed to describe the in-plane deformation for the prismatic beam. A comprehensive kinematic treatment of geometrically exact and nonlinear Cosserat beam subjected to large deformation and finite strain is finally obtained that extensively captures the deformation due to multiple curvatures, torsion, shear, axial deformation, warping and a fully-coupled Poisson’s effect in the cross-section, all while maintaining the single manifold nature of the problem. The contributions to the strain vector and the deformation gradient tensor due to various deformation effects are interpreted and explained in detail. In the final part of the paper, we use the kinematics developed to establish a measurement model of discrete and finite length strain gauges attached to the surface of the beam (or embedded into the beam). We investigate the relationship between the scalar strain measurement of the strain gauge and the local finite strain parameters of the beam.

Kinematic bending of profiles allows to manufacture parts with high flexibility concerning the geometry. Still, the production of profiles with asymmetric cross-sections regarding the force application axis using kinematic bending processes offers challenges regarding springback and warping. These geometric deviations can be reduced by partial, cross-sectional heating during the process as it lowers the flow stress locally. In this work, the influence of partial, cross-sectional heating during a three-roll push-bending process on the warping and springback of L-profiles is investigated. Numerical and experimental methods reveal the influence of temperature on warping and springback. A newly developed analytical model predicts the warping and bending moment in the design phase and assists to understand the effect of warping reduction through partial heating during plastic bending. With increasing temperature of the heated profile area, the warping is reduced up to 76% and the springback of the bend profiles is decreased up to 44%. The warping reduction is attributed to a shift in stress free fiber due to the temperature gradient between heated and room temperature areas. The shift of stress-free fiber leads to an adapted shear center position, resulting in an approximated “quasi-symmetric” bending case.

We develop theory and methodology for the problem of nonparametric registration of functional data that have been subjected to random deformation (warping) of their time scale. The separation of this phase variation ("horizontal" variation) from the amplitude variation ("vertical" variation) is crucial in order to properly conduct further analyses, which otherwise can be severely distorted. We determine precise nonparametric conditions under which the two forms of variation are identifiable. These show that the identifiability delicately depends on the underlying rank. By means of several counterexamples, we demonstrate that our conditions are sharp if one wishes a genuinely nonparametric setup; and in doing so we caution that popular remedies such as structural assumptions or roughness penalties can easily fail. We then propose a nonparametric registration method based on a "local variation measure", the main element in elucidating identifiability. A key advantage of the method is that it is free of any tuning or penalisation parameters regulating the amount of alignment, thus circumventing the problem of over/under-registration often encountered in practice. We provide asymptotic theory for the resulting estimators under the identifiable regime, but also under mild departures from identifiability, quantifying the resulting bias in terms of the amplitude variation's spectral gap., Comment: 54 pages (Accepted for publication in Bernoulli)

This paper presents a three-dimensional beam element for stability analysis of elastic thin-walled open-section beams in multibody systems. The beam model is based on the generalized strain beam formulation. In this formulation, a set of independent deformation modes is defined which are related to dual stress resultants in a co-rotational frame. The deformation modes are characterized by generalized strains or deformations, expressed as analytical functions of the nodal coordinates referred to the global coordinate system. A nonlinear theory of non-uniform torsion of open-section beams is adopted for the derivation of the elastic and geometric stiffness matrices. Both torsional-related warping and Wagner’s stiffening torques are taken into account. Second order approximations for the axial elongation and bending curvatures are included by additional second order terms in the expressions for the deformations. The model allows to study the buckling and post-buckling behaviour of asymmetric thin-walled beams with open cross-section that can undergo moderately large twist rotations. The inertia properties of the beam are described using both consistent and lumped mass formulations. The latter is used to model rotary and warping inertias of the beam cross-section. Some validation examples illustrate the accuracy and computational efficiency of the new beam element in the analysis of the buckling and post-buckling behaviour of thin-walled beams under various loads and (quasi)static boundary conditions. Finally, applications to multibody problems are presented, including the stability analysis of an elementary two-flexure cross-hinge mechanism.

Torsional vibrations in beams are damped by discrete, axial viscous dampers in configurations constituting bimoments. The bimoments act on warping displacements and partial restraining of warping suggests the inclusion of a flexibility parameter, calibrated from numerical results. Correcting for distortion is incorporated in a similar manner. The use of the governing differential equation with calibrated parameters as an alternative to a full complex analysis by a FE model is justified by an example. It is demonstrated that the differential equation determines the damped frequencies and damping ratios with great accuracy. Significant damping ratios of the lowest torsional mode are obtained.

Many satellite-based estimates use gauge information for bias correction. In general, bias-correction methods are focused on the intensity error and do not explicitly correct possible position or timing errors. However, position and timing errors in rainfall estimates can also lead to errors in the rainfall occurrence or the intensity. This is especially true for localized rainfall events such as the convective rainstorms occurring during the rainy season in sub-Saharan Africa. We investigated the use of warping to correct such errors. The goal was to gauge-adjust satellite-based estimates with respect to the position and the timing of the rain event, instead of its intensity. Warping is a field-deformation method that transforms an image into another one. We compared two methods, spatial warping focusing on the position errors and time warping for the timing errors. They were evaluated on two case studies: a synthetic rainfall event represented by an ellipse and a rain event in southern Ghana during the monsoon season. In both cases, the two warping methods reduced significantly the respective targeted (position or timing) errors. In the southern Ghana case, the average position error was decreased by about 45 km by the spatial warping and the average timing error was decreased from more than 1 h to 0.2 h by the time warping. Both warping methods also improved the continuous statistics on the intensity: the correlation went from 0.18 to at least 0.62 after warping in the southern Ghana case. The spatial warping seems more interesting because of its positive impact on both position and timing errors.

A beam-like model is proposed to address nonlinear dynamic response of a thin pipe, under the action of a resonant transverse load. The mechanical model consists of a Timoshenko beam enriched with further kinematic and dynamic variables which, besides extension and bending, consistently describe local effects, related to ovalization and warping of the cross-section. The nonlinear equations of motions are derived via the principle of virtual work, and internal resonance between the global and local modes is addressed by the multiple scale method, after a Galerkin projection of the equations on the first significant modes. The softening behavior induced by the local deformation remarkably affects the asymptotic solution, which turns out to be in good agreement with that provided by numerical integration.

Shrinkage and warping of additive manufacturing (AM) parts are two critical issues that adversely influence the dimensional accuracy especially in powder bed fusion processes such as selective laser sintering (SLS). Powder fusion, material solidification, and recrystallization are the key stages causing volumetric changes of polymeric materials during the abrupt heating&ndash, cooling process. In this work, the mechanisms of shrinkage and warping of semi-crystalline polyamide (PA) 12 in SLS are well investigated. Heat-transfer and thermo-mechanical models are established to predict the process-dependent shrinkage and warping. The influence of raw material- and laser-related parameters are considered in the heat-transfer and thermo-mechanical models. Such models are established considering the natural thermal gradient and dynamic recrystallization, which induce internal strain and volumetric change. Moreover, an experimental design via orthogonal approach is introduced to validate the feasibility and accuracy of the proposed models. Finally, the quantitative relationships of process parameters with product shrinkage and warping are established, the dimensional accuracy in part-scale can be well predicted and validated with printed parts in a real experiment.

This paper presents a finite element analysis of flexural-torsional and buckling behaviour of a thin- walled frame with a special focus on the joint warping behaviour. Four different joint types and two different cross-sections are analysed in order to investigate the influence of warping transmission on the overall behaviour of the structure. External loads are assumed to be static and conservative. The material is assumed to be homogenous, isotropic and linear elastic. The analysis is performed using the MSC Nastran shell model consisting of parabolic shell elements. The results obtained in the analysis together with some typical examples are discussed.

Because of the significance of electron microscope tomography in the investigation of biological structure at nanometer scales, ongoing improvement efforts have been continuous over recent years. This is particularly true in the case of software developments. Nevertheless, verification of improvements delivered by new algorithms and software remains difficult. Current analysis tools do not provide adaptable and consistent methods for quality assessment. This is particularly true with images of biological samples, due to image complexity, variability, low contrast and noise. We report an electron tomography (ET) simulator with accurate ray optics modeling of image formation that includes curvilinear trajectories through the sample, warping of the sample and noise. As a demonstration of the utility of our approach, we have concentrated on providing verification of the class of reconstruction methods applicable to wide field images of stained plastic-embedded samples. Accordingly, we have also constructed digital phantoms derived from serial block face scanning electron microscope images. These phantoms are also easily modified to include alignment features to test alignment algorithms. The combination of more realistic phantoms with more faithful simulations facilitates objective comparison of acquisition parameters, alignment and reconstruction algorithms and their range of applicability. With proper phantoms, this approach can also be modified to include more complex optical models, including distance-dependent blurring and phase contrast functions, such as may occur in cryotomography.

Freeform surfaces need to be discretized into manageable sized panels so that the surface can be fabricated in smaller pieces that are then assembled on site. This discretization process comprises numerous challenges; including not only the aesthetic and spatial concerns, but also the structural and constructional needs. The mesh generated has to fit to the surface, without distorting the form; meanwhile the panels have to preserve their planarity in order to prevent any brittle failure due to warping. This study proposes a unique approach to quadrilateral discretization by incorporating the form, material capacities and fabrication challenges in order to obtain a structure that can be realized and constructed. In this paper, quadrilateral discretization of freeform surfaces is studied with the focus of material properties. The possibility of utilizing quadrilateral meshes with limited non-planarity is explored. The capacity of materials against warping is calculated, by structural experiments and simulations to obtain the limiting values that are integrated into design as tolerance of panels to non-planarity. Consequently, the amount of non-planarity becomes a parameter that needs to be considered during the generation of the quadrilateral mesh in order to generate an optimum surface discretization.

This work investigates the capabilities of two different approaches for the analysis of thin-walled structures, both based on enriched beam theories that include out-of-plane cross-section warping, being the in-plane deformations neglected.

In this paper, the geometry-aware GAN, referred to as GAGAN, is proposed to address the issue of face attribute transfer with unpaired data. The source and target images are not aligned and come from different individuals. The key idea is to deform the source image according to the geometry features and generate a high-resolution image with the desired attribute. To address the problem of the unpaired training samples, the CycleGAN architecture is applied to form an attribute adding and removing cycle, where the bilateral mappings between the source and target domains are learned. The geometry flow and occlusion mask are learned by the warping sub-network to capture the geometric variation between the two domains. In the attribute adding process, the spatial transformer network (STN) warps the source face into the desired pose and shape according to the flow, and the transfer sub-network hallucinates new components on the warped image. In the attribute removing process, the recover sub-network and the STN reverts the sample back to the source domain. Experiments on the benchmarks CELEBA and CELEBA-HQ datasets demonstrate the advantages of our method compared to the baselines, in terms of both quantitative and qualitative evaluation.

Reprojecting raster maps from one projection to another is an essential part of many cartographic processes (map comparison, overlays, data presentation, ...) and reducing the required computational time is desirable and often significantly decreases overall processing costs.The raster reprojection process operates per-pixel and is, therefore, a good candidate for GPU-based parallelization where the large number of processors can lead to a very high degree of parallelism.We have created an experimental implementation of the raster reprojection with GPU-based parallelization (using OpenCL API).During the evaluation, we compared the performance of our implementation to the optimized GDAL and showed that there is a class of problems where GPU-based parallelization can lead to more than sevenfold speedup.

The paper presents a new modeling technique for accurately predicting the complex behavior of thin-walled open and closed section beams made of fiber-reinforced laminated composite materials. The new modeling technique is significantly computational-efficient compared to detailed finite element modeling. In this technique, the complete 3D stress analysis problem consisting of all effects and their couplings is systematically decomposed into a 2D problem applicable to the beam section, and a 1D problem applicable along the beam length. The capability of the technique is not only suitable for thin-walled beams but also applicable for modeling beams with solid, thick-walled sections as well as thin/thick-walled composite beams with in-filled materials. To analyze beams with any arbitrary cross-sectional geometry, a 2D finite element (FE) model is used for solving the 2D sectional problem, while the 1D problem for the global load response of the beams is solved by a 1D FE model utilizing the sectional stiffness parameters obtained from the 2D model. The proposed technique is validated using experimental and numerical results, which show the excellent performance of the model. New results for a range of beam sections are developed using the presented method and validated against detailed FE modeling.

Torsional effects in joints need to be investigated in order to get a complete model of the joint and also to assess the real boundary conditions for the lateral torsional effects in the beams of structural frames. Phenomena such as: torsion, warping, lateral buckling, etc. are usually analysed assuming simplified boundary conditions, namely pinned or rigid, in frame analysis which can lead to erroneous and non-conservative results. With the aim of knowing the correct boundary conditions and real behaviour of the joints under torsion, an experimental program is carried out consisting of two tests of mayor axis doubled extended bolted end plate joints subjected to torsion about the axis along the length of the beam. These experimental results have allowed the validation of the finite element models carried out using the program Abaqus. Once the models are validated models, a parametric study is performed to assess the stiffness and resistance. This study also verifies that these joints behave in a semi-rigid way when compared with the torsional characteristics of the attached beam. Besides, the beam fails prior to the connection in most cases, and therefore, the joints can be assumed to behave as full-strength. Analytical expressions are proposed and checked with the FEM results proving that the proposed analytical formulae and the proposed mechanical model can predict the stiffness quite accurately, with an average error of 8.5%. Despite these joints can be classified as full-strength under torsion, an assessment of their resistance is done as well.

Ionic Polymer Metal Composites (IPMCs) are laminate microstructures composed of an ionic electroactive polymeric membrane plated between two metal electrodes, finding application in actuation and sensing. The IPMC sandwich structure motivates an investigation on the effect of shear deformation on the IPMC behaviour. To reach this goal, we combine the electrochemomechanical framework recently proposed by Cha and Porfiri with the Yu-Krajcinovic structural theory, characterised by a zigzag warping in which the cross-sections of both membrane and electrodes undergo rotations independent of the mid-axis one. This results in an electrochemical response governed by a modified Poisson-Nernst-Planck (MPNP) system of equations nonlinearly modulated by both the curvature and the shear deformation of the membrane. By introducing the Parallel-Plate Assumption (PPA) and resorting to the method of matched asymptotic expansions, we semi-analytically solve the MPNP system and demonstrate, on the basis of a benchmark involving a distributed load, that shear deformation amplifies the sensing response. Our results are validated against two-dimensional continuum finite element simulations, which are further extended to the purpose of providing insight into the role of both the PPA and finite deformations in the presence of shear.

International audience; This paper presents single receiver geoacoustic inversion of two independent data sets recorded during the 2017 seabed characterization experiment on the New England Mud Patch. In the experimental area, the water depth is around 70 m, and the seabed is characterized by an upper layer of fine grained sediments with clay (i.e., mud). The first data set considered in this paper is a combustive sound source signal, and the second is a chirp emitted by a J15 source. These two data sets provide differing information on the geoacoustic properties of the seabed, as a result of their differing frequency content, and the dispersion properties of the environment. For both data sets, source/receiver range is about 7 km, and modal time-frequency dispersion curves are estimated using warping. Estimated dispersion curves are then used as input data for a Bayesian trans-dimensional inversion algorithm. Subbottom layering and geoacoustic parameters (sound speed and density) are thus inferred from the data. This paper highlights important properties of the mud, consistent with independent in situ measurements. It also demonstrates how information content differs for two data sets collected on reciprocal tracks, but with different acoustic sources and modal content. OAPA

This paper presents the formulation of a three-dimensional beam finite element (FE) that accounts for cross-section warping and dynamic inertia effects. The model is the extension of an existing mixed formulation, originally developed for the static analysis of thin-walled beams, to the case of dynamic loading conditions. Four independent fields are considered to derive the element governing equations, i.e. material rigid displacements, strains and stresses and an additional displacement field, describing the out-of-plane warping displacement of the beam cross-sections. The latter is independently interpolated in the element volume by including additional degrees of freedom (DOF) to the nodal translations and rotations classically considered in beam formulations. To obtain a consistent form of the element mass matrix, the cross-section displacement shape functions are computed, relating the generalized cross-section displacement fields to the element nodal variables. In mixed FE formulations, these are not assigned a priori, as in displacement-based approaches, but are derived on the basis of material stiffness and element geometry, together with compatibility conditions. Thus, the Unit Load method is applied to deduce the expressions of the shape functions consistent with the force-based approach, assuming the simply-supported beam as reference element configuration. As opposed to the original FE model, the additional warping DOFs are not condensed-out with the definition of the element quantities but are treated as additional global unknowns. This permits a correct description of the inertia effects and ensures continuity of the warping displacement fields between adjacent FEs. Correlation studies are presented to validate the proposed model and investigate the effects of cross-section warping on the dynamic behavior of thin-walled structures. For selected specimens, the studies compare solutions obtained adopting the proposed beam element with those resulting from shell or brick FE models. Modal decompositions and time-history analyses are conducted, assuming both linear elastic and nonlinear constitutive behavior for the latter.

We study the problem of georeferencing artistic historical maps. Since they were primarily conceived as work of art more than an accurate cartographic tool, the common warping approaches implemented in Geographic Application Systems (GIS) usually lead to an overly-stretched image in which the actual pictorial content (like written text, compass roses, buildings, etc.) is un-naturally deformed. On the other hand, domain transformation of images driven by the perceived salient visual content is a well-known topic known as “image retargeting” which has been mostly limited to a change of scale of the image (i.e. changing the width and height) rather than a more general control-points based warping.

A novel one dimensional beam model for analysis of prismatic thin-walled beams with deformable cross sections is introduced and a novel cross section mode determination procedure, which leads to the three dimensional beam displacement modes, is derived. The first order beam model for linear analysis includes: shear deformations related to both Timoshenko and Mindlin-Reissner type shear deformations, the warping effects of torsion, cross section distortion with related warping effects, as well as the Poisson effect with transverse displacements due to normal stress. The generality of the model allows it to handle open, closed and multi-cell cross sections with branched walls. The cross section analysis procedure leads to two types of beam displacement modes referred to as distortional beam modes and fundamental beam modes, with exponential and polynomial variations along the beam axis, respectively. It turns out that each of the beam deformation modes consists of a sum of one to four cross section displacement fields each with an individual axial variation. The displacement modes can facilitate the formulation of an advanced thin-walled beam element. The beam displacement modes will be illustrated for an open and a closed cross section.

A refined Timoshenko beam model which takes into account warping of the cross sections is presented. The model extends Saint-Venant's theory of uniform torsion to the generic loading of a beam in a coherent manner. The use of kinetic and kinematic assumptions, virtual work expression of full elasticity problem, and the principle of virtual work in derivation brings the presentation to the usual context of engineering models. A new definition of the warping displacement in terms of a variational problem is one of the outcomes. Boundary value problems for the stretch, shear, bending, and torsion loading modes are also given. Analytic and numeric solutions to warping displacements, refined constitutive equations, and correction factors for circular, rectangle, triangle, and open annular cross sections of isotropic material are compared with expressions in literature. As an interesting detail, shear correction factors are found to be purely geometrical quantities, which contradicts many findings in literature.

Structures of the open thin-walled profile are usually designed so to avoid twisting the individual elements. However, for some systems it is impossible to completely prevent twisting due to the torsion of a thin-walled open section, sectional warping due to tightness, additional sectoral stresses. The torsional stiffness of the thin-walled open section of the rod is much higher than their pure torsion rigidity. The structural analysis of the open thin-walled profile can be performed using a finite element shell. This requires careful selection and design of the grid partition and greatly increases the number of nodes and elements in the calculation scheme. Thin-walled rod finite elements can be used to calculate the complex spatial structures of a thin-walled open section with the account of clean and restrained torsion.

Background: Indian noses are broader and lack projection as compared to other populations, hence very often need augmentation, that too by large volume. Costal cartilage remains the material of choice in large volume augmentations and repair of complex primary and secondary nasal deformities. One major disadvantage of costal cartilage grafts (CCG) which offsets all other advantages is the tendency to warp and become distorted over a period of time. We propose a simple technique to overcome this menace of warping. Materials and Methods: We present the data of 51 patients of rhinoplasty done using CCG with counterbalancing technique over a period of 4 years. Results: No evidence of warping was found in any patient up to a maximum follow-up period of 4 years. Conclusion: Counterbalancing is a useful technique to overcome the problem of warping. It gives liberty to utilize even unbalanced cartilage safely to provide desired shape and use the cartilage without any wastage.

An innovative higher-order beam theory, capable of accurately taking into account flexural–shear–torsional interaction, is originally combined with a force-based formulation to derive the corresponding finite element. The selected set of higher-order deformation modes leads to an explicit and direct interaction between three-dimensional shear and normal stresses. Namely, cross-sectional displacement and strain fields are composed of independent and orthogonal modes, which results in unambiguously defined generalised cross-sectional stress-resultants and in a minimisation of the coupling of equilibrium equations. On the basis of work-equivalency to three-dimensional continuum theory, dual one-dimensional higher-order equilibrium and compatibility equations are derived. The former, which govern an advanced form of beam equilibrium, are strictly satisfied via stress fields arising from the solution of the corresponding systems of coupled differential equations. The formulation, which is numerically validated in a companion paper for both linear and nonlinear material response, inherently avoids shear-locking and accurately accounts for span loads. Finally, the superiority of force-based approaches over displacement-based ones, well established for inelastic behaviour, is also demonstrated for the linear elastic case.

The specific features of the proposed force-based formulation derived in the companion paper, which is applied for the first time to higher-order beam theories, are herein thoroughly validated. Introductory numerical examples illustrate the influence of mesh refinement, boundary conditions, and slenderness ratios for isotropic linear elastic response. Specific higher-order effects—unique to the developed element—are then suitably interpreted, as well as the formulation appropriateness to consider distributed loads and to model three-dimensional behaviour, which is verified with solid finite element analyses. Extensive comparisons against existing proposals, namely other refined higher-order beam theories, emphasize the performance of the proposed approach. Finally, the nonlinear response of the element with a multiaxial J2 linear plasticity material model is analysed, highlighting its advantages in relation to a classical force-based Euler–Bernoulli beam using a one-dimensional plastic material model with kinematic hardening.

Wasserstein distances are metrics on probability distributions inspired by the problem of optimal mass transportation. Roughly speaking, they measure the minimal effort required to reconfigure the probability mass of one distribution in order to recover the other distribution. They are ubiquitous in mathematics, with a long history that has seen them catalyse core developments in analysis, optimization, and probability. Beyond their intrinsic mathematical richness, they possess attractive features that make them a versatile tool for the statistician: they can be used to derive weak convergence and convergence of moments, and can be easily bounded; they are well-adapted to quantify a natural notion of perturbation of a probability distribution; and they seamlessly incorporate the geometry of the domain of the distributions in question, thus being useful for contrasting complex objects. Consequently, they frequently appear in the development of statistical theory and inferential methodology, and have recently become an object of inference in themselves. In this review, we provide a snapshot of the main concepts involved in Wasserstein distances and optimal transportation, and a succinct overview of some of their many statistical aspects., Comment: Official version available at https://www.annualreviews.org/doi/full/10.1146/annurev-statistics-030718-104938

This paper describes the simulation of RC members with a three-dimensional (3D), 2-node beam finite element (FE) that includes warping of the cross section. A previously proposed FE formula...

Fused Deposition Modeling (FDM) is the most used 3D printing technology. In this technology, 3D pieces are built warming and extruding thermoplastic through a nozzle. When the thermoplastic gets cold, internal stresses may generate deformations, mainly in corners. In this paper we describe a method for reduce these deformations (called warping), splitting pieces in hexagonal or squared bricks spatially locked. We have developed and tested an application that calculates the necessary GCODE to build the bricking piece directly, and we have measured a significant reduction in warp deformations.

© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works In this paper we present an optimization algorithm for simultaneously detecting video freeze and obtaining the minimum number of the frame required in motion intention estimation for real time robust video stabilization on multirotor unmanned aerial vehicles. A combination of a filter and a threshold is used to the video freeze detection, and for optimizing the algorithm, we find the minimum number of frames for motion intention estimation without decrease the performance.

A class of random non-stationary signals termed timbre x dynamics is introduced and studied. These signals are obtained by non-linear transformations of sta-tionary random gaussian signals, in such a way that the transformation can be approximated by translations in an appropriate representation domain. In such situations, approximate maximum likelihood estimation techniques can be de-rived, which yield simultaneous estimation of the transformation and the power spectrum of the underlying stationary signal. This paper focuses on the case of modulation and time warping of station-ary signals, and proposes and studies estimation algorithms (based on time-frequency and time-scale representations respectively) for these quantities of interest. The proposed approach is validated on numerical simulations on synthetic signals, and examples on real life car engine sounds., Comment: Applied and Computational Harmonic Analysis, Elsevier, 2016, \

International audience; — In passive acoustic monitoring, source localization using multipath propagation can be challenging whenever the source-receiver configuration leads to overlapping multipath arrival patterns. We propose a single-hydrophone model-based method with matched-impulse response (IR) processing that exploits unresolved multipath arrival patterns to locate the source in 3D, making the best use of the bathymetric information as well as the time differences of groups of arrivals. When only groups of paths are resolved, the identity of the paths constituting the groups remains unknown, preventing the use of classical localization methods. To overcome this critical limitation, we apply an approach based on the characterization of groups of paths to estimate the source location.

We propose an approach for multiple sequence alignment (MSA) derived from the dynamic time warping viewpoint and recent techniques of curve synchronization developed in the context of functional data analysis. Starting from pairwise alignments of all the sequences (viewed as paths in a certain space), we construct a median path that represents the MSA we are looking for. We establish a proof of concept that our method could be an interesting ingredient to include into refined MSA techniques. We present a simple synthetic experiment as well as the study of a benchmark dataset, together with comparisons with 2 widely used MSA softwares.

The present paper shows how a non-invasive and low-cost photogrammetric stereo device allows the assessment of morphometric variations of the nose following rhinoplasty. Six female patients, aged between 24 and 37 years, underwent 3D stereo-photogrammetric scanning. Three-dimensional computerised models were generated, extracting also information related to the coordinates of facial landmarks, distances between landmarks, angles, in pre- and postoperative situation. Two kinds of analysis were carried out: (i) statistical correlation between size variations and (ii) morphometric analysis, including General Procrustes Analysis (GPA), Principal Components Analysis (PCA) and Warping. The study shows the usefulness of the stereo-photogrammetric facial digitisation for morphometric analysis of the human face. Three-dimensional computerised models are also an important tool for the assessment of the surgeon's performance in the event of dispute between doctor and patient. Moreover, confirmation of the PCA as an analytical tool for the identification of components characterising the morphometric structure of the nose is highlighted.

Incremental launching is a common and convenient methodology to build continuous girder bridges on several piers. Although it has mainly been applied to straight bridges with box sections, today it is also used for construction of horizontally curved bridges with concrete and composite steel–concrete closed or open sections like I-girders. In these cases the contribution of torsion to the stress state becomes of primary importance when the construction stages of these bridges are analysed. Moreover, the presence of thin-walled cross-sections, makes the analysis of non-uniform torsion fundamental when the angle of twist per unit length is not constant or warping is prevented in those sections where rigid internal diaphragms occur. Consequently the stress state in the launching phases can be strongly influenced by non-uniform torsion, especially for the evaluation of axial stresses in I-girder bridges, where non-uniform torsion presents its maximum influence. In this paper a methodology for the repetitive analysis of launching steps is proposed, based on the Hamiltonian Structural Analysis method, which takes into account the internal characteristics of non-uniform torsion (warping and bimoment) in order to evaluate the influence of prevented warping on the stress state at each stage of launching. The methodology is convenient because it can be considered a sort of generalised beam theory and presents a reduced computational burden with respect to finite element or boundary element procedures, with fast solution of many bridge launching static schemes. A validation of the method is given through a comparison with finite element procedures and literature data. An application is presented on a bridge with different typologies of cross-section in order to compare the different behaviours of thin-walled sections and the different degree of influence of non-uniform torsion on the stress state. The results are given in the form of envelope graphs of internal forces and stresses for the entire launching sequence and for the different cases examined.

We focus on analytic solutions for the accurate computation of the shear stress in sandwich beams under flexure. To this purpose, we follow the strategy recently proposed by our group and apply the Jourawski method to the structural beam model based on the zigzag warping. We consider sandwiches whose cross-section is symmetric with respect to the neutral axis and whose skin shear deformation and core longitudinal stress are accounted for (that is, we do not limit our attention to thin skins nor to antiplane sandwiches). We obtain explicit analytic expressions for the cases of cantilever and propped-cantilever beams subject to uniform transverse load. The comparison with numerical solutions obtained through plane stress finite element simulations shows the excellent accuracy of the analytic solution, apart in a region close to the fully clamped cross-section, where the finite element solution itself is unreliable, while the new analytic solutions provide useful estimates.

International audience; This paper deals with the development of a non-linear finite element model for reinforced concrete members under torsion. Using multi-fiber approach and displacement-based formulation, an enhanced multi-fiber 3D beam is proposed for predicting the behavior of reinforced concrete elements under torsion. The sectional analysis under elastic torsion is considered following Saint-Venant torsional theory for beam in order to take into account the effect of warping phenomenon. Elastic behavior under large displacements is also investigated in this model using a second-order approximation of the Green-Lagrange strains. In the inelastic domain, after cracking, following the space truss theory, the whole element is assumed to act as a tube, meaning the applied torsional moment is resisted only by the shear flow in the wall of the tube. Then, the effective wall thickness of the member after cracking is determined by an empirical formulation developed by the authors. Moreover, the section is discretized into different regions following its material response. In each region, depending on its characteristics, an appropriate constitutive material model is applied. For the concrete, the proposed behavior models are based on the Modified of Compression Field Theory and its extension. In order to correctly predict the torsional response, the authors proposed some modifications in the tensile behavior of concrete, based on experimental tests in torsion. In the elastic domain, the model is validated by comparing to the analytical solution and some results from other researches. In the inelastic field, a good agreement is obtained between a series of experimental tests and numerical results.

International audience; The formal asymptotic expansion method is an attractive mean to derive simpli-fie models for problems exhibiting a small parameter, such as the elastic analysis of beam-like structures. Usually this method is rigorously justifie using convergence theorems Yu and Hodges, 2004. In this paper it is illustrated how the Saint-Venant's solution naturally arises from the lowest order terms of an asymptotic expansion of the elastic state for the case of homogeneous isotropic beams. It is also highlighted that the Saint-Venant solutions corresponding to pure traction, bending and torsion involve the solution of the first-orde microscopic problems, while for the simple bending problem, the solution of the second-order microscopic problems is needed. The second-order problems provide therefore a way to characterize the transverse shear behavior and the cross-sectional warping of the beam.

Free vibration and Ljapounov stability of compressed open thin-walled beams with a cross-section reduction are studied by a in-house finite differences numerical code, based on a refined direct beam model and allowing for investigating elastic stability of non-trivial equilibrium paths in a dynamic setting. The benchmark is a beam with doubly symmetric cross-section and non-zero warping rigidity, under free, semi-, and fully restrained warping at its ends. In all cases, the results of the direct model are compared to finite element and/or experimental ones. The reduction in the cross-section rigidity induces a weakening that may model a local damage; thus, the present investigation may be useful with an outlook to damage monitoring and identification.

Starting with an experiment to authenticate walnut oils based on GC-MS analysis of the volatolome, this paper aims to demonstrate the relevance of a two-step alignment-based strategy for the systematic research of VOC markers. The first step of the treatment consists of roughly reducing the time shifts with efficient, known warping techniques like COW (Correlation Optimized Warping). The second step relies on an accurate peak apex alignment in order to refine residual local misalignments and to enable further systematic marker research through univariate or multivariate data treatments. This two-step strategy was implemented on 117 GC-MS analyses of the volatolome of three vegetable oils with very similar composition. During the analysis campaign, the GC-MS system was intentionally subjected to instrumental drifts in order to generate realistic signal shifts. The first part of this study aims to assess the efficiency of the warping-based strategy in terms of signal alignment and sample discrimination. Whereas no distinction between the three oils was possible with unaligned raw GC-MS data, the application of COW enabled a significant but insufficient improvement of both reduction of temporal drifts and between-group separation with 79% of samples being well-classified according to Linear Discriminant Analysis (LDA). Applying the peak apex alignment procedure to COW-treated signals resulted in a suitable correction of the remaining local distortions and improved the proportion of well-classified samples in LDA to 100%. The second part of this study assesses the robustness of the discriminant markers highlighted in this approach by: (i) discussing the relevance of the best markers involved in the LDA model, where a close review of literature confirmed the consistency for two of them, and (ii) validating highlighted makers by retrieving the set of the 23 markers previously determined by manual processing among those automatically found. The third part shows the potential of the systematic approach for untargeted detection of 184 highly significant relevant markers from the oil volatolome. Finally, the fourth part presents a comparison of our hybrid alignment strategy with two reference alignment methods (iCoshift and STW) in order to assess quality alignment of the GC-MS data and to show the three methods' abilities to detect discriminant markers.

We focus on the description of the stress state of sandwich beams under bending and shear, a non-trivial task if Saint-Venant's principle does not hold, as it is the case if the skins are somewhat stiffer than the core. Each of the analytical structural models available in literature turns out to be accurate for a limited range of relative stiffness between core and skins, or sandwich heterogeneity. For a simply supported sandwich beam subject to uniform transversal load, we evaluate the stress by means of (a) the classical theory relying on the linear cross-section kinematics, appropriate if Saint-Venant's principle holds, (b) the structural theory based on the zig-zag warping (e.g. Krajcinovic D. Sandwich beam analysis. J Appl Mech, Trans ASME 1972; 39(3): 773–778), and (c) the higher-order theory of Frostig et al. (Frostig Y, Baruch M, Vilnay O, et al. High-order theory for sandwich-beam behavior with transversely flexible core. J Eng Mech, Trans ASCE 1992; 118(5): 1026–1043), the latter usually appropriate when the core is much softer than the skins. The results are compared, for several combinations of material and geometrical parameters, with those of finite element simulations in which the sandwich is modelled as a plane stress continuum. This comparison allows us to provide some graphs which can help in selecting the model appropriate for each sandwich heterogeneity. This is accomplished in terms of non-dimensional material and geometrical parameters the sandwich heterogeneity depends on. We identify and discuss two levels of heterogeneity at which one should switch analytical model: one level is related to the validity of Saint-Venant's principle, while the other level is concerned with the definition of antiplane sandwich.

Studies on deformation characteristics of early-age Jointed Plain Concrete Pavements (JPCP) due to environmental effects have drawn significant interest over the years. However, the complex nature of the problem arising from interacting environmental factors has resulted in difficulties in predicting the JPCP deformation characteristics. This study introduces a simplified approach for predicting the early-age deformation of JPCP due to environmental factors using an equivalent temperature difference concept. A newly constructed JPCP section on highway US–30 near Marshalltown, Iowa was instrumented to monitor the pavement response to variations in temperature and moisture during the first seven days after construction. Based on the collected field data, the total equivalent linear temperature difference (ΔTteltd) corresponding to the actual deformation was quantified using Finite Element (FE) based approach, namely ISLAB 2000. The FE-based calculations were compared with the field measured slab deformation properties. Better predictions were obtained when employing a simplified equivalent temperature difference (ΔTteltd) concept for FE based primary response model. Santrauka Pastaraisiais metais ypač domimasi ankstyvojo betono kelio dangos (JPCP) deformacijos charakteristikomis ir poveikio aplinkai tyrimais, tačiau dėl aplinkos veiksnių sąveikos kyla sunkumų prognozuojant JPCP būdingąsias deformacines savybes. Šiame darbe pateikiamas supaprastintas metodas, kaip galima būtų prognozuoti ankstyvojo betono deformacijas JPCP, kylančias dėl aplinkos veiksnių, vartojant ekvivalentinės temperatūros skirtumo sąvoką. Naujai statomame JPCP US-30 plente prie Maršaltauno Ajovoje buvo sukonstruota bandymų įranga ir stebėta dangų reakcija į temperatūros bei drėgmės pokyčius per pirmąsias septynias dienas po statybų pabaigos. Remiantis gautais rezultatais, visų lygiaverčio linijinės temperatūros skirtumų (ΔTteltd), atitinkančių faktinę deformaciją, vertės buvo skaičiuojamos taikant baigtinių elementų (FE) metodą su ISLAB 2000. Apskaičiuotos FE vertės buvo palygintos su natūrinėmis sąlygomis išmatuotomis deformacinėmis savybėmis. Tikslesnė prognozė buvo gauta taikant supaprastintą temperatūrų skirtumo (ΔTteltd) metodiką, grindžiamą pirminiu FE modeliu. Reikšminiai žodžiai: betonas,JPCP,deformacija,baigtinių elementų metodas,temperatūrų skirtumas,dangos analizė ir projektavimas

Large deck openings of ultra large container ships reduce their torsional stiffness considerably and hydroelastic analysis for reliable structural design becomes an imperative. In the early design stage the beam model coupled with 3D hydrodynamic model is a rational choice. The modal superposition method is ordinary used for solving this complex problem. The advanced thin-walled girder theory, with shear influence on both bending and torsion, is applied for calculation of dry natural modes. It is shown that relatively short engine room structure of large container ships behaves as the open hold structure with increased torsional stiffness due to deck effect. Warping discontinuity at the joint of the closed and open segments is compensated by induced distortion. The effective torsional stiffness parameters based on an energy balance approach are determined. Estimation of distortion of transverse bulkheads, as a result of torsion and warping, is given. The procedure is illustrated in the case of a ship-like pontoon and checked by 3D FEM analysis. The obtained results encourage incorporation of the modified beam model of the short engine room structure in general beam model of ship hull for the need of hydroelastic analysis, where only the first few natural modes are of interest.